Arm bone’s tip gets crack (5)
I believe the answer is:
equip
'arm' is the definition.
(arm can mean to equip or supply)
'bone's tip gets crack' is the wordplay.
'tip' indicates one should take the final letters.
'gets' means one lot of letters go next to another.
'crack' becomes 'quip' (both can mean a joke).
The final letter of 'bone' is 'e'.
'e'+'quip'='EQUIP'
(Other definitions for equip that I've seen before include "Provide with requirements" , "Provide with items (for particular task)" , "Give what's needed" , "Give everything needed" , "Accoutre" .)